1. Field of the Invention
The present invention relates generally to an apparatus and method for inserting discrete articles into cartridges. More particularly, the present invention relates to an improved fixture for use with properly inserting staple drivers into cartridges.
2. Description of the Related Art
In the field of microsurgery, a reusable surgical instrument is assembled in well-known conventional fashion where the cutting blade is mounted to traverse a specific pattern guided by elements of the surgical instrument. The blade and associated guide elements are mounted in somewhat remote location with respect to the hands of the surgeon. A conventional feature of the surgical instrument is a staple cartridge which is used only once.
The cartridge is a generally elongated rectangular plastic body which includes a channel formed longitudinally in an elongated body. The channel is a guide for the surgical blade which is secured on the surgical instrument. The structure of the instrument and cartridge which are well-known in the industry includes a plurality of small staples aligned in the cartridge parallel with the guide channel. After the blade makes its cut and other necessary surgical operations are performed, a remote actuator causes each side of the incision to be stapled together for obvious reasons.
The particular structure for manipulating the blade and actuating the staple operation is not a part of this invention and are well-known to one of ordinary skill in the art.
Due to the minute structure involved in the surgery for which this invention is made, there may be as many as fifty or more staples on each side of a two inch incision which are actuated simultaneously to close the wound. Because of the small size of the staples and the drivers in the cartridge for pushing the staples through the tissues against the anvil on the surgical instrument to deflect the points of the staple into a clasping position, the assembling of the drivers into the cartridge and maintaining them in place to drive the staples into the tissues is a labor intensive chore.
The prior art system for mounting the staple drivers in pockets in the cartridge is to form a plastic tree having aligned branches with staple drivers integrally formed on one end of each of the aligned branches. The already-formed conventional cartridge is placed in a fixture and the tree bearing the staple drivers is hand manipulated to place them adjacent the entrance to pockets in the cartridge. Each driver is pressed into the pocket in the cartridge by the fingers of the person doing the assembling. The separation of the individual drivers from the branch of the tree on which it is mounted is accomplished by a flexing of the branches of the tree manually to break off the staple drivers. Then, a hand-manipulated blade or prong is used to press each staple driver down into the cartridge to near the pocket opening on the opposite side of the cartridge.
Unfortunately, the finger operation of pressing each driver into a pocket, the flexing of the branches which also tilts the drivers and the subsequent pressing from the hand operated prongs can misalign some of the drivers within the pockets.
The size of the pockets and the periphery of the drivers may have a slight variation due to the minute structure involved and the fact that both the cartridge and the staple drivers are formed of thermoplastic resin, could cause some play in the assembly and that can cause an alignment problem. Particularly, an inversion of the cartridge could result in some drivers being displaced from their pockets due to gravity and/or impacts during assembly. Obviously, if the staple driver is not in place, there will be no staple at that point in the incision.
Another problem with the assembly is that of misalignment of the staple driver with the cartridge. The tree which holds the staple drivers is inserted into the passages on the fixture. The passages are funnel-shaped so as to attempt to more closely align an individual driver with an individual pocket on the cartridge. However, the use of the funnel-shaped passage does not fully cure the misalignment problem. Because the funnel does not fully engage the driver to be inserted, there is some potential for misalignment which still occurs.
The misalignment of the driver within the pocket can cause additional problems. If the driver is not properly aligned, the staple which is ejected by use of the staple driver may be inaccurately bent in use in surgery. In addition, the misalignment of the staple driver in the pocket can increase the force needed to eject a staple or prevent the activation of that staple entirely.
Yet another problem is the imprecision of separating the staple drivers from the branches of the plastic tree which is referred to as degating. There is a tendency for the remnant of the branch left on the staple driver to be of a random size and often the remnant is larger than desired. The staple drivers are attached to the holder before insertion into the cartridge, but must be removed from the tree before or during the insertion process. The separation of an individual staple driver from the tree leaves some material on a side of the staple driver. While it is not practical to remove all the branch material from the side of the staple driver in the separation process, it is important that the amount of material left on the side be relatively consistent between drivers. The material left on the side tends to cause friction when the staple driver is used in surgery. If the amount of material left is relatively consistent, it allows a user of such a staple cartridge to accurately predict the amount of force needed to expel a staple in surgery. In addition, the smaller the volume of material left, the less friction will be generated, and the less the force required to use the staple cartridge, which is beneficial in a surgical procedure.